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Linear Actuators: what they're and how to choose them

 

A linear actuator is a self-supporting structural system capable of transforming a circular motion generated by a motor right into a linear motion along an axis. Helping to produce movements such because the pushing, pulling, raising, lowering or inclination of a load.

 

 

The most typical use of actuators includes combining them with multi-axis Cartesian robot systems or using them as integral elements of machines.

 

 

The main sectors:

 

industrial automation

 

servos and pick-and-place systems in production processes

 

assembly

 

packaging and palletisation

 

Indeed, just think of applications akin to aircraft, laser or plasma slicing machines, the loading and unloading of machined pieces, feeding machining centres in a production line, or moving an industrial anthropomorphic robot alongside an additional exterior axis with a view to expand its range of action.

 

 

All of these applications use one or more linear actuators. In accordance with the type of application and the performance that it must guarantee by way of precision, load capacity and velocity, there are various types of actuators to select from, and it is typically the type of motion transmission that makes the difference.

 

 

There are three important types of motion transmission:

 

 

belt

 

rack and pinion

 

screw

 

How can you make sure that you select the correct actuator? What variables does an industrial designer tackling a new application have to take into consideration?

 

 

As is commonly the case when talking about linear motion solutions, the important thing is to consider the problem from the fitting viewpoint – namely the application and, above all, the results and performance you might be expecting. As such, it is worth starting by considering the dynamics, stroke size and precision required.

 

 

Let’s look at these in detail.

 

 

High Dynamics

 

In many areas of industrial design, equivalent to packaging, for instance, the calls for made of the designer fairly often have to do with speed and reducing cycle times.

 

 

It's no surprise, then, that high dynamics are commonly the starting point when defining a solution.

 

 

Belt drives are sometimes the best solution when it comes to high dynamics, considering that:

 

 

they permit for accelerations of up to 50 m/s2 and speeds of as much as 5 m/s on strokes of so long as 10-12m

 

an X-Y-Z portal with belt-driven axes is typically capable of dealing with loads ranging from extraordinarily small to approximately 200kg

 

according to the type of lubrication, these systems can provide notably lengthy maintenance intervals, thus guaranteeing continuity of production.

 

Wherever high dynamics are required on strokes longer than 10-12m, actuators with rack and pinion drives tend to be a wonderful solution, as they permit for accelerations of as much as 10 m/s2 and speeds of up to 3.5 m/s on potentially infinite strokes.

 

 

The choice of a special type of actuator would not guarantee the identical outcomes: a screw system, which is undoubtedly a lot more exact, will surely be too slow and would not be able to handle such long strokes.

 

 

Lengthy Strokes

 

Systems created by assembling actuators in the typical X-Y-Z configurations of Cartesian robotics usually, in applications corresponding to pick-and-place and feeding machining centres alongside production lines, have very long strokes, which may even reach dozens of metres in length.

 

 

Plus, in many cases, these lengthy strokes – which often involve the Y axis – are tasked with handling considerably heavy loads, often hundreds of kilos, as well as numerous vertical Z axes which operate independently.

 

 

In these types of applications, the best choice for the Y axis is unquestionably an actuator with a rack and pinion drive, considering that:

 

 

thanks to the inflexibleity of the rack and pinion system, they're capable of operating along doubtlessly unlimited strokes, all whilst maintaining their inflexibleity, precision and effectivity

 

actuators with induction-hardened metal racks with inclined teeth which slide alongside recirculating ball bearing rails or prismatic rails with bearings are capable of handling loads of over a thousandkg

 

the option of putting in a number of carriages, every with its own motor, allows for numerous independent vertical Z axes.

 

A belt system is ideal for strokes of as much as 10-12m, whilst ball screw actuators are limited – in the case of long strokes – by their critical speed.

 

 

Positioning Repeatability

 

If, on the other hand, the designer is seeking most precision – like in applications such as the meeting of microcomponents or sure types of dealing with within the medical discipline, for instance – then there is only one clear choice: linear axes with ball screw drives.

 

 

Screw-driven linear actuators supply the very best efficiency from this standpoint, with a degree of positioning repeatability as high as ±5 μ. This efficiency cannot be matched by either belt-driven or screw-driven actuators, which both reach a maximum degree of positioning repeatability of ±0.05 mm.

Sito web: https://www.firgelliauto.com/collections/linear-actuators

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